The present invention relates to a technique effective in application to a display drive control device to drive a display device as well as a display drive control device incorporated into a semiconductor integrated circuit, specifically to a technique effective in use for a liquid crystal display drive control device to drive a collar liquid crystal panel used in a portable electronic device such as a mobile telephone, and an electronic device such as a mobile telephone using the same.
There has been developing a trend of using a dot-matrix liquid crystal panel having multiple pixels arrayed in matrix two-dimensionally in the display of a portable electronic device such as a mobile telephone or a PDA (Personal Digital Assistant), and in the electronic device is loaded with a liquid crystal display control device (liquid crystal controller) incorporated into a semiconductor integrated circuit that controls the display of the liquid crystal panel, a liquid crystal driver that drives the liquid crystal panel under the control of the control device, or a liquid crystal display drive control device (liquid crystal controller driver) containing the liquid crystal controller and the liquid crystal driver.
Most of the conventional liquid crystal panels used in the portable electronic devices display black-and-white still-picture images. However, the contents displayed on the still-picture images. However, the contents displayed on the panels are increasingly diversified accompanied with the recent trend for higher functionality in the portable electronic devices, and colored or animated displays have become a main current.
In this trend, some electronic devices having color liquid crystal panels display images of information of characters and symbols on parts of background images in a transparent state, utilizing the advantage of the color display, or generate reduced image data on the basis of the image data stored in the memories by means of the resizing function, thus displaying multifarious images through processing of the original image data. Conventionally, it has been a general exercise to carry out these processing through the software of a microprocessor mounted on an electronic device.
The trend for color display or large display in the liquid crystal panel accompanies increase of image data, and the introduction of animated displays involves increase of the contents of processing that a microprocessor is demanded to carry out. Accordingly, when the data processing for a transparent display is carried out through the software of a microprocessor, the microprocessor is required to have high functionality and high-speed processing capability, which invites increase of the system cost as well as prolongs the time from starting the processing till actually presenting the transparent display.
Besides, when the data processing for a transparent display is carried out through the software of a microprocessor, provided that the transparency of first image data is given by α, it is necessary to carry out the processing that multiplies α to the first image data, multiplies (1−α) to the second image data, and further adds these results (hereunder, called α blending); thus the contents of processing cannot be relieved of complexity.
The processing for a transparent display by the software will inevitably involve reading out the original image data stored in an external memory, processing the data, and sending the data to a liquid crystal controller driver LSI; accordingly, a repeated execution of a transparent display and a non-transparent display will require the microprocessor to read out the image data from the external memory and send the display data to the liquid crystal controller driver LSI, each time the display is switched, which will unavoidably increase the power consumption and processing time.
A liquid crystal controller driver LSI mounted on a portable electronic device incorporates a memory for storing image data displayed on a liquid crystal panel in many cases, and the trend for color display or large display in the liquid crystal panel will require enlarging the capacity of the built-in memory. However, to enlarge the capacity of the built-in memory will lead to not only increasing the chip size, but also raising the chip cost, which requires an efficient memory management technique for realizing a desired display with a comparably less memory capacity.
Further, there has recently appeared a mobile telephone having liquid crystal panels on both the inside and outside of the body thereof. In such an electronic device as having two liquid crystal panels, to provide a liquid crystal controller driver LSI corresponding to each of the liquid crystal panels will extremely raise the cost. Accordingly, there arises a demand for a technique capable of driving the two liquid crystal panels with one liquid crystal controller driver LSI. However, efforts to realize the liquid crystal controller driver LSI capable of driving the two liquid crystal panels will invite many problems to be solved, for example, increase of the storage capacity that the memory requires, suppression of the power consumption in case of the display of either panel being unnecessary, and so forth.